Department of Microbiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran.
BMC Microbiol. 2024 Sep 28;24(1):365. doi: 10.1186/s12866-024-03521-z.
The emergence of Streptococcus agalactiae infections in patients with bacteremia is increasing. It is crucial to investigate the epidemiology, molecular characteristics, biofilm status, and virulence analysis of Streptococcus agalactiae in these patients.
In this cross-sectional study, 61 S. agalactiae isolated from blood infection were subjected to characterization through antimicrobial susceptibility tests, biofilm formation, multilocus sequence typing (MLST), and PCR analysis for detecting resistance (tet and erm family) and virulence genes (alp2/3, alp4, bca, bac, eps, rib, lmb, cylE, and pilus island genes).
Overall, 32.7% of the isolates demonstrated an inducible clindamycin resistance phenotype. The results showed that 49.2, 24.6, and 8.2% of confirmed Streptococcus agalactiae strains were classified as strong, intermediate, and weak biofilm-forming strains, respectively. tet(M) (57.1%) was recovered most, followed by tet(M) + tet(L) (14.3%), tet(S) + tet(K) (10.7%), tet(M) + tet(K) (8.9%), tet(M) + tet(K) + tet(O) (5.4%), and tet(S) + tet(L) + tet(O) (3.6%). Three virulence gene profiles of cylE, lmb, bca, rib (24.6%; 15/61), cylE, lmb, rib, alp3 (19.7%; 12/61), and cylE, lmb, bac, rib (16.4%; 10/61) were detected in approximately two-thirds of the isolates. MLST revealed that the 61 isolates belonged to six clonal complexes, including CC1 (49.2%), followed by CC12 (18%), CC19 (13.1%), CC22 (9.8%), CC17 (6.6%), and CC283 (3.3%), and 11 different sequence types (STs), including ST1 (24.6%), ST7 (14.8%), ST918 (13.1%), ST2118 (9.8%), ST19 (9.8%), ST48 (6.6%), ST1372 (4.9%), ST22 (4.9%), ST40 (4.9%), ST734 (3.3%), and ST283 (3.3%). Remarkably, all CC1 and CC12 isolates, three-fourths of CC19, and half of CC22 were confirmed as biofilm producers. Conversely, CC17 and CC28 isolates were found to be nonproducers. The occurrence of strong biofilm formation was limited to specific CCs, namely CC1 (34.4%), CC12 (8.2%), CC19 (3.3%), and CC22 (3.3%).
The high prevalence of CC1 and CC12 clones among S. agalactiae strains reflects the emergence of these lineages as successful clones in Iran, which is a serious concern and poses a potential threat to patients.
血源感染性无乳链球菌感染的出现正在增加。对这些患者的无乳链球菌的流行病学、分子特征、生物膜状态和毒力分析进行研究至关重要。
在这项横断面研究中，对 61 株从血液感染中分离出的无乳链球菌进行了特征分析，包括抗菌药物敏感性试验、生物膜形成、多位点序列分型（MLST）以及检测耐药性（tet 和 erm 家族）和毒力基因（alp2/3、alp4、bca、bac、eps、rib、lmb、cylE 和菌毛岛基因）的 PCR 分析。
总的来说，32.7%的分离株表现出诱导型克林霉素耐药表型。结果表明，49.2%、24.6%和 8.2%的确认无乳链球菌菌株分别被归类为强、中、弱生物膜形成菌株。tet(M)（57.1%）是最常见的，其次是 tet(M) + tet(L)（14.3%）、tet(S) + tet(K)（10.7%）、tet(M) + tet(K)（8.9%）、tet(M) + tet(K) + tet(O)（5.4%）和 tet(S) + tet(L) + tet(O)（3.6%）。大约三分之二的分离株中检测到 cylE、lmb、bca、rib（24.6%；15/61）、cylE、lmb、rib、alp3（19.7%；12/61）和 cylE、lmb、bac、rib（16.4%；10/61）三种毒力基因图谱。MLST 显示 61 株分离株属于六个克隆复合体，包括 CC1（49.2%），其次是 CC12（18%）、CC19（13.1%）、CC22（9.8%）、CC17（6.6%）和 CC283（3.3%），以及 11 个不同的序列型（STs），包括 ST1（24.6%）、ST7（14.8%）、ST918（13.1%）、ST2118（9.8%）、ST19（9.8%）、ST48（6.6%）、ST1372（4.9%）、ST22（4.9%）、ST40（4.9%）、ST734（3.3%）和 ST283（3.3%）。值得注意的是，所有 CC1 和 CC12 分离株、四分之三的 CC19 和一半的 CC22 被确认为生物膜产生者。相反，CC17 和 CC28 分离株被发现为非生产者。强生物膜形成的发生仅限于特定的 CC，即 CC1（34.4%）、CC12（8.2%）、CC19（3.3%）和 CC22（3.3%）。
CC1 和 CC12 克隆在无乳链球菌菌株中的高流行率反映了这些谱系作为成功的克隆在伊朗的出现，这是一个严重的问题，对患者构成潜在威胁。
